Add Ansible Galaxy Proxy support

With Ansible 2.10, Ansible Galaxy is going to increase its role as a primary "repository" from which you can download community features (so called "collections" and "roles").

With this ticket, I would like to see being able to proxy such repository - i.e. similarly to nuget proxy, maven proxy, docker proxy, etc.

Collections/roles are then downloaded using ansible-galaxy (https://docs.ansible.com/ansible/latest/cli/ansible-galaxy.html)

Hosted type would be (for me) non-essential - but always welcome.